Making bearings



Oct. 27, 1936- R PIKE I 2,058,621

MAKING BEARINGS Filed Feb. 5, 1934 2 Sheets-Sheet 1 ENI/ENTOR.

ATTOR Ys..

Oct. 27, 1936. R. D. PIKE 2,058,621

MAKING BEARINGS Filed Feb. 5, 1954 2 Sheets-Sheet 2 24C/ ii; 30A

INVENTOR. Yfinfmitlfllh. BY I3 W E ATTORNEYS.

Patented Oct. 21, 1936 UNITED STATES PATENT OFFICE:

MAKING BEARINGS Robert 1). Pike, Piedmont, Calif., assignor to nu: Corporation, Emeryville, Calii'., a corporation of Delaware Application February 5, 1934, Serial No. 109,113-

'IClaims.

My present invention relates to the manufacture of compound castings, usually for bearings, in which plastic bronze is cast-welded to steel or other ferrous metal backor core.

' Objects of my present invention are:

To reduce the differential cooling stresses between the cast-welded plastic bronze and the 1 ferrous back; I

To increase the number of unit articles, usually bearings, which can be produced at one round of casting; and

Other objects which are brought out in the following specification and drawings. The plastic bronze covered by my present invention includes the so-called pure copper-lead alloy containing from 20% to 50% of lead, less than 1% of other elements, and the balance copper; and also includes those alloys also containing 20% or more of lead, the balance being various alloys containing a major amount of copper with various minor amounts of tin, nickel, and/or other metals. However, experience has shown that an alloy of practically 70% of copper and 30% of lead, with less than 1% impurities, as wellas the other alloys included above, may have imparted thereto by my process exceptional anti-friction properties not hitherto obtainable with such al loys. I shall describe my invention as r'elating particularly to this alloy by way of illustration, but not by wayof limitation.

, In the drawings which form part of this spec'i ficationa Fig. I is a vertical section of a set-up which I may use;

Fig. 2 is a sectional view of a cover which is employed in a phase of the cooling process;

- Fig. 3 shows a series of set-ups on the hot plate be provided to direct the metal to the holes 20.

on which the casting is done;

Fig. 4 is a' plan view of the water-quenching apparatus accommodating a series of set-ups; 60 Fig. 5 is a sectional view of Fig. 4, showing the first of arow of set-ups on the quenching stand;

Fig. 6 is a sectional view showing the appearance of a casting after solidification shrinkage has been substantially completed; Fig. 7 is a sectional view showing certain phenomena which occur thereafter during waterquenching; and

Fig. 8 is a vertical section of a modified set-up. I shall now describe for the purpose of descrlp-- tion,-but not for limitation, the application of my :5

process to the making of steel-backed bearing blanks, lined with an alloy of 30% of lead, balance copper, with less than1% of other metals or impurities, securely welded to the steel backs.

I take a soft steel tube l0, preferably with car- 10 bon content less than 2%, and machine it into the form of a series of backs, usually three'in number. The outside of the tube is roughly turned to a shape corresponding to the finished bearings,

, and the recesses H are cut out with an inside cut- 15 ting tool. These recesses have slightly sloping tops and bottoms and all comers are rounded. A thin piece of joining metal I! is left, as well as bottom and top extensions l3. The connections I2 and extensions iii are, of course, machined off when 20 the casting is turned into the form of finished bearings. The clear vertical height of the recesses H is usually made about %-inch in excess of the amount of. metal which has to be left finally on the faces of the flanges. A core of lit-gauge 25 sheet steel is rolled and welded along its longitudinal seam, and isthen welded at I8A' onto the bottom plate I! which is then welded at l8 to the bottom extension l3. This gives the so-called back-core set-up, which will be referred to simply 30 as the set-up. For the usual automotive bearing, the diameter of the core is preferably. chosen with reference to the inside diameter of the steel back so that the annulus or casting space is about 54;- inch on a radius. Experience has shown-that this gives a practical amount of metal so thatwhen the core and sheet metal are machined out a perfeet-bearing surface is left.

Casting heads I!) are preferably made of. a refractory alloy of iron, chromium and nickel.

'Ihese are set into the open upper end of the core tube l6, whose upper edge is slightly higher than the upper edge'of the extension l3. The pouring head is cup-shaped and is provided with the holes 20 which direct the flux and molten metal into 5 the casting annulus 2|. A central boss 2IA .nay

In carrying through my process, I prefer to handle six such set-ups with casting heads in 7 place in a batch, because with the usual size of set-upsv for automotive bearings, this gives ,a proper timing for the steps of the process to be described. These are put into a high-speed, gasfired furnace, not shown, of conventional type and, heated very rapidly in a neutral'to reducing to atmosphere to 850 to 950 C. (1562 to 1742 F.)

such heating usually taking 5 to 10 minutes. I then find it convenient to transfer the set-ups to an electric resistance furnace of conventional design of the same temperature as the gas-fired furnace and to hold them for 3 to 5 minutes to even up the temperature. This entire heating process minimizes the formation of scale, al-

though no attempt is made entirely to prevent its hot by the gas burner 23. This is merely to avoid chilling the lower ends of thes et-ups, which, if it occurred, would cause some flux to be trapped in the bottom of the set-up.

In the meantime, a pot of the 70/30 alloy has been melted and brought to a casting temperature of 1100 C. to 1200" C. (2012 F. to 2192 F.),

preferably employing the method described in my Patent No. 1,910,446, issued May 23, 1933; and simultaneously a supply of molten flux has been brought to a highly superheated temperature of 1400" C. to 1500 C. (2552 F. to 2732 F.). I

prefer to use as a flux the following combination:

Per cent Anhydrous borax 80 Crynlite 1O Boric acid 10 although other mixes may be employed. This mixture melts at a little below 600 C. (1112 F.) and at this temperature of superheat which I employ is extremely fluid. It also has a strong dissolving action for oxide of iron and at the same time is not severely corrosive on the refractory pots in which Iusually melt it.

As the set-ups are placed upon the hot-plate in sequence, the highly superheated fiux is poured into the casting annulus of each in turn, filling the same, the men carrying the hot fiux pot filling each set-up in turn as it is placed on the hot plate by another operator. This has the effect of dissolving all of the iron oxide and in raising the average temperature .of the back about 100 F., although the inside face of the back immediately adjoining the flux is at a somewhat higher temperature and is in a very active condition chemically. In effect, the superheated fiux is utilized to bring the inside surface of the back to a welding temperature, tocleanse it, and to activate it chemically; and also to act as a refining and cleansing agent for the cast metal which is poured through it in. several small streams from the casting head. It should be remarked in this connection that the flux which I employ has-a strong dissolving action for copper oxide and lead oxide, as well as for iron oxide. I have also found it advisable to stir the flux with a graphite rod beforepouring so as to metal, the whole pouring operation for the six set-ups usually taking from 30 to seconds. Each set-up is filled full of metal so that a little spills over the edge of i3. When each set-uphas been filled with metal, they are removed from the hot-plate and placed on the quenching stand upon the platforms 25. The transfer from hot plate to quenching stand should be made while the metal is fully liquid to avoid the possible disturbance of partially formed dendrites of cop:- per. 1

It should be noted at this point that neither the back itselfas a whole nor the poured-in copper-lead is hot enough, in itself, to cause welding. Yet perfect welding does occur simultaneously with the pouring of the copper-lead and this is caused by the superheated fiux, which heats a surface film of the steel back to a considerably higher temperature than the average temperature of the back. It should also be noted that this welding is due to instantaneous wetting of the steel by the copper component of the copper-lead and is not accompanied by any appreciable alloying of the steel back with the copper-lead,- which results in the latter usually containing only from a trace to .3% of iron as a maximum, an important factor in obtaining the best anti-friction properties. The reason for this is very specific and based upon well known metallurgical laws. At room temperature copper will hold in solid solution only about 1% of iron, and lead and iron are mutually immiscible at all temperatures. Therefore, if a /30 copper-lead alloy contains 30% of iron, the copper constituent of the' alloy is ,fully saturated with iron and has therefore been considerably hardened and rendered abra-- sive, Also, any iron content above 370% will appear in the alloy as a constituent of iron with about 1% of copper in solid solutiontherein and this will be a hard abrasive material. Hence it is of highest importance to keep the iron content as low as possible and I accomplish this bythe use of superheated fiux causing instantaneous welding by wetting without alloying or solution, and by directing the poured metal into streams by means of the casting head, for the greaterthe contact of the cast metal with the way' I minimize the contamination of the cast metal with iron by erosion.

, Furthermore, the steel is wetted onlyby the copper constituent of the copper-lead alloy, and this fact, coupled with the method of chilling about to be described, results in the commence immediately in contact with the steel of a weldedon layer of copper about .001-inch thick, from which all lead has been expelled, probably by the phenomena of surface tension. Where'the plastic bronze contains other constituents, as .tin or alloy of copper with such constituent.

The quenching stands or racks comprise preferably a base plate 24 having an up-standing flange 24A all around the edge thereof to collect the water which drops down, and an outlet B to drain off the collected water. the table members 25 which are intended to support the set-ups. By reason of the process herein described, it is possible to quench a gang of, say

six castings simultaneously, and with this in view I provide quench rings 30, preferably one for each set-up. These quench rings are usually made of a ring of %-inch coppertubing about '7 inches in diameter when automotive bearings are nickel, the steel back is generallywetted by the Pillars 240 support being made, 'each quench ring being perforated with a number of %-inch holes 30A, which direct the water slightly downwardly toward the center.-

Each ring is connected by a pipe 303, having an individual valve 300 therein, to a supporting and water-supplying manifold 30D, which in turn is connected by a flexible pipe, as a hose, ME to a source of water supply controlled by the master valve 30F. The manifold and rings may be attached to any suitable mechanism, not shown, for moving upand down so as to cover the entire outside surfaces of 'the set-ups, or any part thereof, or none at all, at the option of the operator.

Immediately after the set-ups have been placed on the quenching rack, the casting heads I9 are removed in the order of placing on the rack. In the meantime, the hats or covers 26, which are preferably made up of -inch steel plates 21 and skirts of 16-gauge sheet steel 28 have been brought to about the same temperature to which the backs had been brought in the gas-fired furnaee before pouring ,the flux. These hats or covers are placed on the tops of the set-ups, as shown by the dotted lines in Fig. 1, immediately after removal of the pouring heads and in the same order as their removal. Taking the pouring of metal into the first set-up as the starting time, the last placed hat or cover is removed in about 100 to 150 seconds, and the balance are removed in the reverse order of their placing. This reversal of order serves to some extent to even up the temperature of the setups, a certain disparity of temperature having been brought about by the fact that the last set-up poured has necessarily cooled for the shortest time and is therefore the hottest. By removing the covers, which slow up cooling, in reverse order, the set-ups receiving the metal last will tend to receive a little extra cooling, and their temperatures at the beginning-of the water quenching will be substantially the same as that of those set-ups receiving the cast metal earlier.

Although these covers are only in place for a comparatively short time, they serve an important purpose in that they prevent the premature and/or non-uniform solidification of the metal in the top space N. This metal is relied upon to feed the casting as it shrinks on solidification and it is therefore of great importance to have the casting in this preliminary cooling stage cool from the bottom toward the top and to have the metal at the top freeze last. This has several important results, notably, it prevents the formation of cracks, it prevents the formation of sink holes in the top of the casting, which in the absence of the covers may be as small in diameter as a pencil and from. one to two inches deep, it gives the best possible opportunity for the escape of., gas, and it gives the copper crystals an opportunity for effecting a strong, close interlock in dendritic formation amongst themselves uniform- 'ly throughout the casting.

When the covers have been removed, the metal in the top should still be in the liquid condition and the removal of the covers exposes the tops of usually be in from to 200 seconds after 'pour ing metal into the first set-up. j

Instructions for water-quenching can not be given as a precise schedule but certain principles are involved, the correct application of which by one skilled in the art is a part of my process, In general I have found it advisable to extract the heat quite'uniformly from the set-up as a whole without at the same time causing too steep temperature gradients within the casting. It is preferable to move the quench ring up and down over the outside of the casting several times, or for 30 to 40 seconds before raising it above the casting and allowing water to play on the top and for some to flow down the core. This helps to form and set thelayer of copper welded to iron or steel to which I have referred and to drive the lead away from the iron-copper interface for an appreciable but very slight distance. It is not advisable to use too great a water pressure back of the spray so as to avoid setting up too great temperature gradients within the casting, one pound per square inch usually being ample.

More care is required in quenching flange bearings than-straight bearings without flanges, parshown in Fig. 6 which has heavy flanges after an improper application of the water quench. In

this'case, the metal toward the core and the top in the area 3| remained too hot with reference to the balance of the casting during the first stage of water-quenching. The copper crystals in the cooler metal in the lower part of the casting 32 interlocked more strongly than those in the upper, hotter part 3!, and this caused an actual movement upward of lead from the more strongly interlocked or cooler copper crystals into the region of less strongly interlocked, hotter copper crystals. At the same time gas from the cooler portions passed into theupper'portions. The combined movement of gas and lead caused a pronounced massive exudation of leadrich metal 33 on top of the casting, and when the latter was machined a bad area of lead segregation would be noted in the area 3| and usually extending into the metal of the flanges.

The operator who controls the quench learns to so operate the movement of the quench as to permit enough secondary movement to' level off the casting to the line 34, and a properly quenched casting will have such a level surface substantially at the original level of theliquid metal, and the surface will be covered with leadrich metal of grey appearance. If, an operator notes the beginning of a formation like 33 mga casting,,which I call a blow, then he raises the quench to the upperpart of the set-up and usually can stop the blow? before it spoils the casting. Ordinarily the water spray is left on for 100 to seconds before the set-ups are cold enough to handle; A properly quenched casting with a fiat to necessarily denotes that, a strong internal pressure has existed at' the moment of complete 75 rigidity and this internal pressure is important for three reasons:

(1) It tends to counteract the differential 'contraction stresses which necessarily arise between the copper-lead and the steel because of the fact that the former has a much greater coefficient of thermal expansion than the latter. Thus, in a properly quenched casting, the tendency for ,distortion of the bearing after splitting is virtually eliminated and it is unnecessary to rely upon mechanical deformation to remove differential stresses as covered in Patent No. 1,945,294, issued January 30, 1934. This expansion from the position shown at 29 to that shown at 34 enables'me to .cast a series of flanged bearings end to end of total-.length as great as 15 inches or more without crack formation due to longitudinal differential contraction between the cast metal and the steel.

(2) The dendritic copper crystals, each'of which is completely surrounded with an envelop of lead, are strongly pressed together and locked securely against being torn away from the bearing surface in service. This is one of the important features of my invention which results in the production of copper-lead castings of hitherto unexcelled anti-friction properties. If the copper crystals are too fine and not securely locked in the structure of the casting, minute crystals are torn away as the shaft rotates in the bearing causing grooving of the shaft even though the shaft be of heat-treated hardened steel. But in bearings made by myprocess, the copper crystals have first been able to form fully developed dendrites by slow cooling to a certain point, and

thus these dendrites are compressed strongly together by properly conducted and controlled water-quenching.

(3) The lead is uniformly distributed around each copper crystal or dendrite, giving a uniform distribution of its essential anti-friction properties.

Summing up, my method of quenching consists' ofmetal to be cast-welded to the steel backings.

.cient secondary movement of the metal to restore the level of the casting to substantially or nearly its original liquid level, thus creating an internal pressure in the casting and strongly compressing and locking the copper dendrites, and

counteracting thermal stresses caused by differential shrinkage of steel and copper-lead.

Another method of avoiding the difliculties of drastic chilling above referred to is 'to retard or mask the chilling effect in such manner as to flatten out the temperature gradients within the plastic bronze. This is illustrated in Fig. 8

wherein the steel backing is shown as thicker or heavier, the undesired part of the steel being cut away after cooling of the casting; this cuttingaway being along the dotted lines 35. In this figure three independent backing rings 36, 31 and 38 are shown, these being joined together by welding the connecting rings 39 and 40 thereto to form, with the core IS, the casting space 2| for the Sheet metal pieces ll, H, are likewise welded, respectively, to the upper-end of the upper'backing and to the lower end of the lower backing to functionsimilarly to the parts l3 of Fig, 1. As in said figure, a bottom plate l1, having an open-' ing A, is welded at I 8 to the lower end of the ring 42, and at IDA to the lower end of the core It.

In this connection it may be stated that it is not necessary to have the backing members independently formed and then joined together by welding of the sheet metal rings above described, but the set-up may be made of one continuous piece of steel, as in the modification of Fig. 1, it being understood, however, that the exterior concavities HA of said figure may be decreased or eliminated entirely to have the metal of the backing thicker. Conversely, if desired, the setup of Fig. 1 may be modified to eliminate the joining pieces l2 thereof and to substitute therefor the welded-on bands of sheet metal described with respect to Fig. 8.

With the backings thicker than necessary, for the purpose of controlling the cooling effects it is preferable to do most, if not all, of the cooling from the outside and very little,'or none, from the inside of the core. The total temperature drop in the thicker set-up resulting from the outside cooling will thus be more in the steel and less in the plastic bronze, whereby the temperature gradient in the plastic bronze may be reduced by increasing that in the iron or steel back, with the rate of quenching sufliciently rapid to meet all requirements. I have found in a number of cases that having the temperature gradients in the backing equal tdor greater than those in the plastic bronze, will, as ageneral rule, give the desired results.

Bearings made by my method are in wide commercial use and are the only backed copper-lead bearings which have been successfully employed as replacement bearings on-automotive shafts of ordinary commercial machines without causing more than normal shaft wear. In many instances bearing life has been increased from 20,000 miles to in excess of 200,000 miles by the use of my bearings in long-transport automotive engines.

Having described my invention, what I claim and desire to secure by Letters Patent is-- 4 1. The process of cast-welding plastic, bronze onto an iron or steel backing which comprises heating a group of backing set-ups, each set-up comprising a casting head and a series of backs red thereby, pouring into the set-ups superheated flux capable of dissolving any scale formed, pouring molten plastic bronze into said set-ups through andto replace said flux, permitting to cool slowly while maintaining the top of the casting at least as hot as any other part thereof, and chilling rapidly when the trough at the top of the casting'resulting' from cooling acquires its maximum depression, while filling said trough to substantially its original level by controlling said rapid chilling.

2. The process of cast-welding plastic bronze onto an iron or steel backing which comprises heating a group of backing set-ups, each set-up comprising a casting head and a series of backs fed thereby, to a temperature of about 850 to 950- C., each to the same temperature, under conditions to form a scale, easily removable by the flux hereinafter referred to, removing said set-ups in sequence to a heated plate, pouring into the set-ups in the same sequence superheated flux at about 1400 to l500 C., pouring,plastic bronze at a temperature of about 1100 to 1200 C. into said set-ups in the same sequence through and to replace said flux, said bronze being poured directly toward the bottoms of said set-ups, removing said bronze-filled set-ups in the same sequence to a quenching stand while said bronze is fully liquid, removing the casting heads in the same sequence and substituting therefor in the same sequence hats heated to about the temperature of said set-ups. allowing to stand for a time to permit slow and even cooling and to cause the metal at the top to freeze last, removing said hats in reverse sequence while said metal at the top is still liquid, chilling rapidly when the trough at the top of the casting resulting from cooling acquires its maximum depression, and controlling the chilling as to intensity and as to parts of the casting to cause substantial filling of said trough to its original level.

3. The process of cast-welding plastic bronze onto an iron or steel'backing which comprises heating a group of backing set-ups, each set-up comprising a casting head and a series of backs fed thereby, to a temperature of about 850 to 950 C. in a gas-fired furnace providing a neutral. toreducing atmosphere, evening up the temperatures of said setups, removing said set-ups in sequence to a heated plate, pouring into the setups in the same sequence superheated flux at about 1400" to 1500 C. and comprising, substantially,

' Per cent Anhydrous bor x Cryolite i .10 Boric acid 10 pouring plastic bronze at a temperature of about 1100 to 1200 C. into said set-ups in the same sequence through and to replace said flux, said bronze being poured directly toward the bottoms of said set-ups, removing said bronze-filled setups in the same sequence to a quenching stand while said bronze is fully liquid, removing the casting heads in the same sequence and substituting therefor in the same sequence hats heated to about the temperature of said set-ups, allowing to stand for a time to permit slow and even cooling and to cause the metal at the top to ireeze last, removing said hats in reversesequence while said metal at the top is still liquid, chilling rapidly when the trough at the top of the casting resulting from cooling acquires its maximum depression, and controlling the chilling as to intensity and as to parts of the casting to cause filling of said trough substantially to its original level.

4. The process or cast-welding plastic bronze onto an ironor steel backing which comprises heating said backin pouring thereonto and maintaining thereon superheated flux capable oi. dissolving scale formed on said backing, pouring molten plastic bronze into said fiux to replace the same, permitting to cool slowly while maintaining the top of the casting at least as hot as any other part thereof, and chilling rapidly when the trough at the top of the casting resulting from cooling acquires substantially its maximum depression, while causing filling of said trough substantially to its original level by controling said chilling.

5. The process of cast-welding plastic bronze onto an iron or steel backing which comprises heating a group of series of backing set-ups, pouring into the set-ups superheated fiux, pouring molten plastic bronze into said set-ups through and to replace said flux, permitting to cool slowly with faster cooling below than above, chilling rapidly when the trough at the top of the casting resulting from cooling acquires its maximum depression, and filling said troughsubstantially to its original level by controlling the chilling.

6. The process of cast-welding plastic bronze onto an iron or steel backing which comprises heating said backing, pouring thereonto and maintainingthereon superheated flux capable of removing scale formed by saidheating, pouring molten plastic bronze into said flux to replace the same, permitting to cool slowly with faster cooling below than above, chilling rapidly when the t'rough at .the top of the casting resulting from coolingacquirsnubstantiallyim maximum H depression, and filling said trough substantially to its original level by controlling said rapid chilling.

7. The process of cast-welding plastic bronze onto an iron or steel backing which comprises heating said backing to a temperature of about 850 to 950 C. under conditions to form a scale easily removable by the hereinafter mentioned ,fiuz, pouring thereonto and maintaining thereon superheated flux at a temperature of about 1400 to 1500 C., pouring plastic bronze at a temperature of about 1100 to 1200 C. through said flux to replace the same, said bronze being poured to points away from said back, allowing to stand for a timeto permit slow and almost even cooling to maintain the cast metal slightly hotter above than below, chilling rapidly when the trough at the top of the casting resulting from cooling acquires substantially its maximum depression. and filling said trough substantially to its original level by controlling said chilling.

ROBERT D. PIKE. 

